Among motorcycles having a supercharger are ones having a turbocharger which uses an engine exhaust gas as a drive source of the turbocharger. In such motorcycles, an exhaust manifold is attached to exhaust ports of a cylinder head and the turbocharger is attached to the exhaust manifold.
Usually, turbochargers are lubricated properly by supplying part of oil that circulates the engine to a drive portion of the turbocharger (refer to JP-UM-A-61-47436, for example). JP-UM-A-61-47436 discloses a turbocharger lubrication structure in which oil that is pumped up from an oil pan is supplied to a main gallery via an oil cooler and an oil filter. Oil is supplied to the turbocharger from a passage that branches off from an oil passage located upstream of the oil cooler.
In engine lubrication structures in general, oil is pumped up from an oil pan by an oil pump and supplied to individual components of the engine via an oil passage that branches off from a main gallery. Among such engine lubrication structures are ones in which oil is supplied from a main gallery directly to shaft bearings where high oil pressure is necessary (refer to JP-UM-A-4-107543, for example). JP-UM-A-4-107543 discloses an engine having a 2-axis balancer structure in which balancer shafts are disposed in front of and in the rear of a crank shaft. Oil passages to the bearings of the front and rear balancers and the bearings of various transmission shafts branch off from a main gallery where the oil pressure is high.